The present invention concerns a technology for conveying parts by aligning them in prescribed orientation by preventing passage of parts placed upside down. More specifically, this technology can be utilized for aligned conveyance of parts with projection the protruding part of which is formed on either the upper side or the lower side as seen in the direction of height as with a projection nut.
In the case where projection nuts having projections for welding, for example, are fed from a parts feeder, the projection nuts are arranged in a certain orientation of surface or back face before going out of the parts feeder. However, there are cases where the parts are fed out upside down for some reason or another and, to prevent them from being fed in a wrong state, a control method is known which consists in detecting the height of the parts and letting pass normal parts only while stopping unusual ones.
In the case where the two sides are discriminated based on the height of the parts conveyed, control may be easy if there is an appreciable difference in height between the parts looking upward and those looking downward but, if the difference in height is inappreciable, it is necessary to delicately adjust the space in height of the member which regulates the parts. For example, a projection nut generally has projections for welding formed at 4 corners of a square nut, and the quantity of protrusion in the direction of height of each projection is comparatively small while, in the direction of breadth, a quantity of protrusion larger than that in the direction of height is set. Therefore, in the case where the two sides are discriminated based on the height of parts, fine adjustment of the regulating member is rather difficult and even a slight deviation of adjusted value may make the discrimination impossible, thus letting pass parts which are placed upside down. Moreover, in the case of parts having hardly any difference in height between the upward looking state and the downward looking state, it is simply impossible to perform any control of passage based on the parts height.
According to an embodiment of the present invention, the method for conveying parts comprises the steps of connecting a parts feeder to a parts supply unit, providing a parts transfer passage for transferring parts with projections the protruding part of which is formed on either the upper side or the lower side as seen in the direction of height, disposing, at a position close to the parts feeder of the transfer passage, a regulating member for preventing passage of a part placed upside down in the case where such part is transferred, disposing a parts sensor at a position close to the supply unit of the transfer passage, detecting, with the parts sensor, reduction in the number of parts on standby between the parts sensor and the supply unit in the case where the passage of parts is prevented by the regulating member, operating the parts feeder with this detection signal, and issuing an abnormality signal in case no part is detected by the sensor after passage of a certain time from that operation.
By issuing a signal, with such operation, in case no supply of parts on standby is started even with passage of a certain time after the passage of parts placed upside down is prevented by the regulating member, it becomes possible to either give an alarm such as buzzer or lamp, etc. by using this signal or stop the operation of the parts feeder, and this is effective for reduction of noise and saving of electric power. In case no supply of parts on standby is made with passage of a certain time while the parts feeder continues working, it is possible to either stop the operation of the parts feeder or give an alarm to notify an abnormality by judging that the parts are prevented by the regulating member, and thus take remedial measures such as removal of unusual parts, etc.
According to another embodiment of the present invention, the method for conveying parts comprises the steps of connecting a parts feeder to a parts supply unit, providing a parts transfer passage for transferring parts with projections the protruding part of which is formed on either the upper side or the lower side as seen in the direction of height, disposing, at a position close to the parts feeder of the transfer passage, a regulating member for preventing passage of a part placed upside down in the case where such part is transferred, disposing a parts sensor at a position close to the parts feeder of the transfer passage and on the downstream side of the regulating member, and issuing, in the case where the passage of parts is prevented by the regulating member, an abnormality signal in case no part is detected by the sensor after passage of a certain time after the part immediately before the prevented part was detected by the parts sensor. Here also, an abnormality signal is issued in case a part is prevented by the regulating member, and it becomes possible to either give an alarm such as buzzer or lamp, etc. or stop the operation of the parts feeder by using this signal, and this is effective for reduction of noise and saving of electric power.
According to other embodiment of the present invention, the apparatus for conveying parts is designed for transferring parts with projections the protruding part of which is formed on either the upper side or the lower side as seen in the direction of height by aligning them in prescribed orientation, and comprises a regulating member for preventing passage of a part transferred in the state upside down. The regulating member performs regulation and control in response to the protruding part formed on either the upper side or the lower side of the part, and allows passage of parts in normal orientation only. Therefore, passage of parts placed upside down can be prevented without fail.
The regulating member may have a regulating portion of a width for preventing passage of the protruding part of the part, and a non regulating portion of a width allowing passage of the protruding part disposed at the top and at the bottom. This makes it possible to prevent passage of a part placed upside down the protruding part of which is caught by the regulating portion. On the contrary, in the case where the protruding part corresponds to the non regulating portion, the part is allowed to pass through. By thus installing the regulating portion and the non regulating portion in a fixed way, it becomes unnecessary to make any fine adjustment as in the prior art, and this helps to greatly improve the working accuracy and simplify the daily control at the same time. Furthermore, even in the case where there is hardly any difference in height of the parts whether they are placed in the upward looking direction or downward looking direction, passage of any parts in unusual direction can be prevented because of the relation between the regulating portion and the non regulating portion, enabling application to a wide range of parts with high utility.
The apparatus may comprise a sorting device disposed on the upstream side of the regulating member, and the sorting device not only guides the parts in linkage with the projections of the parts but also sorts out the parts by discriminating the surface and the back face of the parts and dropping parts placed upside down. The sorting device may be constructed with a portion in which the outside of the spiral passage is low, and a groove of a fixed length formed in the direction of transfer of parts in the spiral passage. The apparatus may comprise a collecting box for receiving parts dropped by the sorting device, the collecting box communicating with the inside of the bowl of the parts feeder.
The apparatus may comprise an unusual nut discharging device disposed on the upstream side of the sorting device, the discharging device being composed of the portion in which the outside of the spiral passage is low, an upright wall provided on the outer circumference of the portion, an opening formed in the upright wall, and an accumulating box, positioned below the opening, for receiving unusual parts dropping from the opening. In the case where the height of unusual parts is smaller compared with the normal parts, it is desirable to set the height of the opening higher than the unusual parts but lower than the normal parts.
According to still other embodiment of the present invention, the apparatus comprises a parts feeder, a sorting device for discriminating the surface and the back side of parts transferred through the spiral passage of the parts feeder and discharging parts placed upside down, and a discharging device disposed on the upstream side of the sorting device.
The sorting device may be constructed with a portion in which the outside of the spiral passage is low, and a groove of a fixed length formed in the direction of transfer of parts in the spiral passage. The apparatus may further comprise a collecting box for receiving parts discharged by the sorting device, the collecting box communicating with the inside of the bowl of the parts feeder.
The discharging device may be composed of a portion in which the outside of the spiral passage is low, an upright wall provided on the outer circumference of the portion, an opening formed in the upright wall, and an accumulating box, positioned below the opening, for receiving unusual parts dropping from the opening. In the case where the height of unusual parts is smaller compared with the normal parts, it is desirable to set the height of the opening higher than the unusual parts but lower than the normal parts. Unusual parts are made to drop into the accumulating box by the discharging device, not to be mixed into normal parts. In this way, unusual parts are prevented from being sent to the downstream processes.
In the case of unusual parts the height of which is smaller than that of normal ones, discharge of unusual parts can be made accurately by utilizing the difference of height. The unusual parts discharging device is characterized in that it is provided with an opening of a height enabling passage of unusual parts but preventing passage of normal parts. In this way, unusual parts are sorted out and discharged in the state where a difference of height is detected accurately. Especially, since discharge of unusual parts is made on the upstream side of the point of discrimination of surface and back face, delivery of unusual parts is prevented even when the unusual parts are placed in the correct orientation. As an unusual part comes to the control board, this unusual part passes through the opening and drops into the accumulating box to be kept there, because its height is smaller than that of the opening. Therefore, even in case some unusual part is returned by error into the bowl of the part feeder, it eventually passes through the discharging device and is caught in the accumulating box, thus preventing delivery of any defective parts.